Not to open up another can worms, but there is differences in sound heard from a blank CDR burned on a home computer and one burned on a stand alone CDR recorder. And yes even when using "Exact Copy".
Since the CD copy should normally be a bit perfect copy (you can confirm this easily using a computer), you may want to invest in a better CD player or DAC. What you are experiencing are differences in sound quality due to small differences in the media disc such as weight, color, coating, central hole alignment, balance of the disc etc. - normally a good player will be immune to such differences - it should read the bits correctly without affecting the built in DAC and low jitter clock:it should result in identical sound.